Resistance unit



F. FREYMAN RESISTANCE UNIT Oct. 17, 1933.

Filed Aug. 29,' 1930A l ffy.;

@VVV/xl Patented Oct. 17, 1933 UNITED STATES PATENT Ioi-FiclazApplication August 29, 1930. Serial No. 478,649

3Claims.

This invention relates to resistance units, and more particularly toresistance units which are provided with fiat rectangular cores.

Heretofore in the manufacture of a certain 5 flat type of resistanceunitl used in telephone systems. the resistance wire wound on a core hasbeen connected to the binding posts secured to the lateral edges of thecore by means of intermediate stranded terminal wires which have )eenthreaded into apertures of the core and connected to the ends of theresistance wire by twisting, splicing, and' iinally trimming theconnection.

AThe primary object of this invention is to provide a resistance unit ofsimple, durable, and

inexpensive construction.V

In accordance with this object, one embodiment of the inventioncomprises a resistance unit consisting of a flat core of partially curdphenolized insulating material, preferably phenolized asbestos, which isnotched at its lateral edges to provide four corner stop lugs betweenwhich p the resistance wire is wound. The ends of this resistance wireare soldered to spaced, nat terminal clips which are clamped inapertured portions of the core. Both sides ofthe wound core are coveredwith sheets of phenolized asbestos slightly wider than the core which donot re quire preheating for their application, and binding posts areclamped over both` lateral edges of the core and covers at the same timethat' the opposite nat sides of the unit are subjected `topressureandtheunitisheatedtobakeand curo the phenoliccondensation product. The notcheson the lateral edges of the core between Jthe stop lugs aiford spaceinto which the pheno lined material ows for properly insulating the fturns of resistancewire from each other and v from vthe lateral bindingposts. The flat termi- 40 nal clips are attached to the binding posts byl soldering.

These and other objects of the invention appear from the followingdescription of one specific embodiment thereof as illustrated in theaccompanying drawing, wherein unisg. 1 is a side view of the completedresistance Fig. 2 is a side ,view of thecore thereof; Fig. 3 is an endview of the'core showing the v150' left end terminal clip thereto:

Fig. d is a central cross-section view of the core taken on the of Fig.3, and showingacentralterminalclipclampedarolmdthis portion;

,.65 Hg,5lsasideviewofthephenolinedasbestos sheet used to cover thefront side of the resistance unit as viewed in Fig'. 1:V

Fig. 6 is a side view of a sheet of similar material used to cover therear side of the unit, and

Fig. 7 is a central cross sectional view of the nished unit taken on theline 'l-'I of Fig.- 1 to show the abutting of the lateral edges of thesecover sheets againsteach other underneath the binding posts clampedthereover.

Referring now to the drawing in which like reference numerals designatesimilar parts throughout the several views, the contemplated resistanceunit includes a flat rectangular core 10 consisting of partially curedphenolized in- 70 sulating material, preferably phenolized asbestos, andthis core is notched 'at its lateral edges to provide four corner stoplugs 1l--ll. The resistance wire l2 is wound around the core 10 betweenthe stop lugs 11--11 in a single layer 75 of separated, helical turnslin order that the turns may not contact and short circuit each other,and in the case of the particular resistance unit disclosed, theresistance wire l2 is not wound over the central portion of the core 10,but the wire terminates at that point for making an external connection.Of course it will vbe understood that so far as the invention isconcerned connections may be made at varionspoints along the core 10;that is, the wire 30 may be wound into various numbers of sections.

'lhis wire 12 is terminated at each end of the core 10 by soldering endsof the wire to a pair o f similar iiat terminal strips or clips 13-13`which are clamped to the core. As shown in 90 Fig. 3, the clips 134-13are clamped'tothe core by inserting one end 14 of each' f theclipsthrough apertures in the core and then bending these ends againstthe flat surface of the corel The opposite ends 15 are simply bentaround the edge 95 V74of the core and against the fiat surface thereof.

Both of the clips 13` are similarly clamped in position, except that inthe illustration the right end clip 13 is shown attached to the loweredge of the core whereas the left hand clip 13 is secured to 100 the topedge of the core. It is not important to the invention which edge of thecore the clips are attached to orin what relative direction their endsare bent, the essential feature being that these clamping clips 13 arereadily clinched 1.05 to the core and it is a simple matter to connectlthe ends of the resistance wire 12`thereto, since the resistance endsare simply soldered to the clips.

A central clip 16,

similmto the cups '1s-1a 11GV is shown secured to the center of the core10, the clip being shown attached to the core in this instance simply byinserting both ends 17 and 18 of the clip, as shown in Fig. 4, throughspaced apertures in the core and then bending or clamping these endsdown against one flat surface of the core. The inner ends of theresistance Wire l2 are shown soldered to the two ends of the clip 16, i

After the clips have been secured in the aforementioned manner the woundcore `l0 is covered on each side by partially cured phenolized covers orsheets 19l and 20 of insulating material, which may be` phenolizedasbestos the same as the core l0. The sheets 19 and 20 are of about thesame thickness as the core 10 but, as shown in Fig. 7, their widthslightly exceeds that of the core so that the lateral edges of thesesheets somewhat overlap the edges of thefcore in order that the edges ofthe sheets just abut against each other, as shown at 21 and 22. By usingsheets of such a width just exceeding the width of the core, the sheetsdo not have to be preheated before they are applied to the core as hasheretofore been the practice in some instances. In the next step of themanufacture of the unit after the core is covered with the sheets, apair of binding posts 24-24 are inserted over the lateral edges of theassembled core l0 covered with the sheets 19 and 20, and pressure plates(not shown), slightly narrower than the width of the resistance unit,are placed against and applied to both at surfaces of the unit. The unitis heated to bake and cure it, and said pressure plates simultaneouslyclinch the inner edges of binding posts 24-24 to the insulatingmaterial, as shown in Fig. '7. This pressing andbaking of the assembledunit converts the phenolized covers 19 and 20 and the core 10 into ahomogeneous structure which encloses and embeds resistance wirer 12, andthe recess or notch on each lateral edge of the core 10 between the stoplugs l1-l1 becomes filled with phenolized material to insulatethoroughly and completely the binding posts 24-24 from the resistanceWire and the turns of resistance wire from each other.

Corner portions of the sheet 19 are cut out as shown at 25-25 to providespaces for a contact between the tei-minal eiips 13-13 and the bindingposts 24-24 where the adjacent terminal clips and binding posts may besoldered to each other, as shown in Fig. 1. A central aperture 26 isprovided in the sheet 19 when the central terminal clip 26 is used, anda central binding post 27 (Fig. 1) is, as the last step of themanufacture, clamped at its ends' to `the ends of the assembly andsoldered to the central. terminal clip 16. The binding post 27 issecured in position simply by bending clamping portions at its endsaround the ends of the covers 19 and 20 and core 10. If labels are to beattached to the covers 19 and 20, the preferable method is to glue themthereto while the covers are still in strip form before the covers areassembled in the unit. This then completes the manufacture and providesan assembled unit as shown in Fig. 1.

Although phenolized asbestos is preferably used as the material for thecore and covering sheets, since the asbestos gives the unit sufficientbody and strength and is incombustible, and such phenolized material hasa suiciently high melting point to resist heat in service and at thesame time may be cooled suciently rapidly to make the manufacturecommercial, it will be noted that other fibrous materials may beemployed which are impregnated with suitable materials, such as varnish,shellac, natural or artificial resins, and\ so on, without departingfrom the spirit and scope of the present invention.

It will also be noted that the notch or recess located in each edge ofthe core 10 between the end stop lugs 1l (Fig. 2) allows suihcientmelted phenolized material to flow therein to adequately insulate theturns of the insulating wire 12 eX- tending around the edges of the corefrom each other, and also to fully insulate these portions of theresistance wire from the lateral binding posts 24-24. It will also beremembered that the flat terminal clips 13-13 and 16 are readilyclinched to the core 10 and provide a simple means for terminating theresistance wire. Furthermore it will be noted that the phenolized sheets19 and 20 which are slightly wider than the core 10 do not have to bepreheated to be applied. It is therefore believed to be apparent thatthe invention produces a simple and eiiicient resistance unit.

It will of course be understood that the invention is not limited to thespecific embodiment herein illustrated and described, but is limitedonly by the scope of the appended claims.

What is claimed is:

1. A resistance unit comprising a flat rectangular core of phenolizedinsulating material, resistance wire wound on the flat core, flatterminal clips clamped about spaced apertured portions of the core andconnected to the ends of the resistance wire, a pair of phenolizedinsulating covers for the wound core having their lateral edges justabutting each other at the lateral edges of the core, and a pair ofbinding posts clamped and secured over the abutting edges of the covers,and secured to the terminal clips.

2. A resistance unit comprising a core, a resistance element wound onthe core, a clip on each end of said core, an insulating sheet on eachface of said core, one of said sheets having Windows overlying saidclips, binding posts clamped over the lateral edges of said sheets, anda connection extending through said windows between each of -said clipsand one of said binding posts.

3. A resistance unit comprising a flat core ofI insulating material,resistance wire wound thereon, a pair of insulating covers for the woundcore having their lateral edges abutting along the sides of the core,and a pair of binding posts clamped over the abutting edges of' thecovers and electrically connected to the resistance wire.

FRED FREYMAN.

